1. Field of the Invention
The present invention relates to a lithography step in steps of manufacturing a semiconductor device, and particularly to a pattern data verification method for a semiconductor device for determining whether an allowable error for design data of a pattern formed by using two or more masks falls within an appropriate range by using simulation, a computer-readable recording medium having a pattern data verification program for a semiconductor device recorded, and a semiconductor device manufacturing method for forming a pattern by using two or more masks.
2. Description of the Related Art
In recent years, a manufacturing technique for a semiconductor device has been remarkably developed, and semiconductor devices each having a minimum process size of about 70 nm have been mass-produced. Micropatterning of the semiconductor device has been realized by the remarkable progress of micropattern forming techniques such as a microprocess technique, a photolithography technique, and an etching technique. In a previous generation in which a pattern size of an integrated circuit is sufficiently larger than that in the present generation, a planar shape of a desired integrated circuit pattern formed on a wafer is directly written as a design pattern, and a mask pattern faithful to the design pattern is formed. The mask pattern is transferred onto a wafer by a projection optical system, and an underlying layer to which the mask pattern has been transferred may be etched. In this manner, the integrated circuit pattern almost equal to the designed pattern can be formed on the wafer. However, with the advance of micropatterning of the integrated circuit pattern, a pattern is difficult to be faithfully formed in each manufacturing process of a semiconductor device, which therefore makes it disadvantageously difficult to obtain an integrated circuit pattern of a desired design pattern size.
In particular, in a key lithography process and etching process to achieve micropatterning, a layout or an arrangement of another pattern arranged around a pattern to be formed considerably influences the dimensional accuracy of the pattern to be formed. Therefore, techniques such as a so-called optical proximity correction (OPC) and process proximity correction (PPC) have been developed to avoid the above influence. These techniques appropriately correct a pattern size by adding an auxiliary pattern in advance or increasing or decreasing the width of the pattern to make the size of a processed pattern equal to the values of the desired design pattern. The techniques have been reported by, for example, Jpn. Pat. Appln. KOKAI Publication Nos. 9-319067 and 2003-107664, or SPIE Vol. 2322 (1994) 374 (Large Area Optical Proximity Correction using Pattern Based Correction, D. M. Newmark et al.). By using these techniques, an integrated circuit pattern written by a designer can be formed almost according to the design pattern.
However, when these correction techniques are used, a new technique to verify these corrections is required. As a method of verifying a correction, a method of performing verification on the basis of a specification value of an actually formed mask pattern is conceived as an example. However, in order to accurately verify the correction, verification using a lithography simulator is necessary. For example, in a technique disclosed in U.S. Pat. No. 6,470,489 B1, there is proposed a verification tool which compares an edge portion of a desired pattern on a wafer and an edge portion of a pattern transferred by using a layout of a pattern to which optical proximity correction has been applied with each other by simulation to check whether a difference between the edge portions falls within a range of a predetermined allowable value. In the technique disclosed in Jpn. Pat. Appln. KOKAI Publication No. 9-319067, there is proposed a method for performing optical proximity correction and preparing a physical model for verification to accurately predict a positional difference between an edge portion of a desired pattern and an edge portion of a transferred pattern by simulation.
The “predetermined allowable value” used in these verification methods means an allowable value which is uniformly set for an integrated circuit pattern regardless of positions or line widths of the integrated circuit pattern or which is set for each position or each line width of the integrated circuit pattern. Alternatively, the “predetermined allowable value” means an allowed size variable which is regulated in advance for each part of an integrated circuit pattern such as each element of a transistor or each end portion of a line pattern. There is also a method of performing correction on the basis of each allowable value or each allowed size variable. These methods are techniques for determining an allowable range for a pattern by simulation on the basis of design data of integrated circuit patterns described by all designers.
In regard to such techniques, in recent years, a technique using a mask, called a Levenson type phase shift mask, is now beginning to be applied to the steps of manufacturing a mass-produced semiconductor device. This technique uses two masks having different opening shapes and different phases to obtain a final pattern shape on a wafer. The technique is different from a conventional technique in that two masks are used. However, since the two masks are used, the following two problems are posed. As one of the problems, the correctness of a pattern shape on a midstream stage cannot be assured by setting an allowable range based on a pattern shape on a wafer on a final stage. As the other of the problems, the correctness of a pattern shape on a wafer on a final stage cannot be assured by an allowable range based on a pattern shape formed from only one of the masks.
In the Levenson type phase shift mask, it must be noted that a portion between openings being different from each other in phase by 180° and a portion between openings being equal to each other in phase have different resolutions. More specifically, in the Levenson type phase shift mask, the resolution of the portion between the opening having a phase of 0° and the opening having a phase of 180° is higher than the resolution of the portion between openings each having a phase of 0° or the resolution of a portion between openings each having a phase of 180°. For this reason, even though patterns formed on a wafer have equal sizes, portions of the resist shapes are different from each other. As a result, portions of a process shape of a final pattern formed on a wafer are different from each other disadvantageously.
Therefore, when a Levenson type phase shift mask is used, in consideration of not only a pattern forming portion but also a phase difference between openings formed in the mask, an allowable range for the pattern needs to be independently set. However, such technique did not previously exist. More specifically, in a pattern forming step using the conventional Levenson type phase shift mask, an allowable range for a pattern to be formed is so wide that a defective portion is easily missed. Or, conversely, in the pattern forming step using the conventional Levenson type phase shift mask, an allowable range to a pattern to be formed is so strict that the processing time becomes too long, thus the throughput decreases.